Source:http://linkedlifedata.com/resource/umls/id/C0030004
MSH: Five-membered heterocyclic ring structures containing an oxygen in the 1-position and a nitrogen in the 3-position, in distinction from ISOXAZOLES where they are at the 1,2 positions.,CSP: five-membered heterocyclic ring structures containing an oxygen in the 1-position and a nitrogen in the 3-position.